The present invention relates to an IC test instrument which is suitable for use, for example, in probe-testing semiconductor chips.
Probe needles for probe-testing are generally made of tungsten.
In a probe test of semiconductor chips, the tungsten probe needle incorporated in a probe card undergoes an enormous number of repetitive contacts, through the needle point, with semiconductor chips. The service life of the tungsten probe needle is about one million operations. As the probe needle tip repetitively comes in contact with aluminum pads formed on the semiconductor chip, aluminum oxide sticks to the end of the probe needle, increasing the contact resistance. The adhesion of aluminum oxide is caused as follows. In the process of manufacturing the tungsten probe needle, a tungsten oxide film is formed in the surface of the tungsten. But since the strength of the tungsten oxide film is weak, the tungsten oxide film is broken by the repeated contact with the aluminum pads, allowing the pure tungsten to come into direct contact with the aluminum pads. As a result, aluminum adheres to the tungsten and oxidizes.
Since the probe test cannot be continued when the contact resistance of the probe needle becomes large, it is necessary to polish the tip of the probe needle every several tens of thousands of contacts to remove the aluminum oxide. This requirement is a hindrance to the performance of automatic, continuous probe testing on a large number of semiconductor chips.